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It depends how long you're planning to keep the car or sell it before the next service and some other poor git has to have the 'plug drilled out and helicoiled :-)
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Cement £5, helicoiling £xxx!
Cement fails, engine down to 3 cylinders, possible damage to ECU = £xxx. Not to mention the inconvience of having to wait for a breakdown truck; that is if the artic lorry hasn't wiped you out beforehand by you trying to get from lane 3 to the hard shoulder.
Helicoiling isn't that expensive, and not outside the scope of the average DIY'er who's willing to havea go themselves.
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A good professional engineering firm can do the helicoil without removing the head.
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I had a helicoil in my sump for £30, while it was on the car.
What you can try, ir geting an old plug, and cutting a two grooves at 90?deg to the threads and 180?deg apart, use some oil on it, and use it as a tap, turn it in a turn then back half a turn, then forward half a turn, until it's right in, then unscrew and put the new plug in.
or try www.jbweld.com/
and permanently bond a uridium plug in, should last the life on any Cavalier!
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I used to do that but without the bonding.never had any probs
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Richard,
Loctite 243 (Nutlock) retaining compound would hold the plug OK so long as there is still a bit of resistance to turning. This grade of Loctite would also allow removal using the normal spanner. However there is a very big 'IF' ...
If the head is an aluminium alloy, this won't activate the Loctite into curing unless it contains at least 2% copper (and this is very unlikely). If the spark plug thread is zinc plated, that won't readily activate curing either.
Loctite needs the exclusion of oxygen AND the direct presence of copper or ferrous ions to activate it. In the absence of one or other of these ions, an activating fluid can be used. The activator is a copper compound in solution and it works quite well, however it needs applying very thinly but must thoroughly cover at least one of the surfaces. It also reduces the strength of the Loctite by typically 15%.
As I said, Loctite 243 will allow the plug to be removed. The problem here is that you will need to apply more torque than normal to undo the plug and this is likely to damage the already weak threads even more. Given all these 'ifs' and 'buts' I think it has to be a helicoil in this case.
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To use locking compound you will have to temove the plug and if it is crossed or stripped that may be the end of it and a helicoil is the only way to go. Regards Peter
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Thanks, friend. JB Weld sounds good. What's an iridium plug?
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To meet 100,000 miles service intervals, spark plugs with iridium alloy electrodes have been developed. If a plug were to be glued permanently in place (horrendous bodge in my opinion!), a long life plug would be preferable.
If trying out one of these adhesive/cement products please be aware that the ceramic insulator (nose) of the spark plug absorbs heat from the combustion process, and likes to reject approx 70% of this heat to the head, via the "motor seat". (This is the interface between the spark plug body and the cylinder head). If this heat path is impaired (e.g. plug not torqued in), under high power output, the ceramic nose might overheat and put that cylinder into pre-ignition. With 3 other cylinders keeping the works going round, it can make quite a mess before you notice the loss of power.
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